JPS5933911Y2 - cryopump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The invention consists of a cooling wall for trapping by condensation and a wall for trapping by adsorption coated with at least one layer of adsorbent material such as activated carbon or zeolite. The present invention relates to a cryopump of the type in which a capture device having a capture device is provided in a thermally insulated enclosure.

The combination of these two trapping walls allows theoretically 10” due to the fact that gases such as hydrogen or neon, which are difficult to condense even at extremely low trapping pressures, are trapped by the walls for trapping by adsorption. - Extremely high vacuums on the order of 100 mm can be achieved.

However, the efficiency of the wall for trapping by adsorption is
This is considerably reduced by the fact that it is contaminated by easily condensable gases such as nitrogen, oxygen, and argon.

It has been demonstrated that this drawback can be alleviated by placing the trap-by-adsorption wall downstream of the trap-by-condensation wall in the gas flow; This can be achieved by including a wall forming a baffle to shield the wall for trapping by adsorption from direct gas impingement.

Baffles of this type have at least three drawbacks.

First, it is expensive to manufacture, and second, even if it were to be effective in molecular flow conditions, it would need to be optically sealed, with the result that the pumping velocity of the adsorbent-coated surface would be reduced. Finally, in situations where the gas flow within the enclosure is viscous or intermediate, as occurs in some applications of cryopumps, no matter how designed, the adsorbent It has no protective effect.

Another method of evacuation by adsorption is to deposit on the cryo surface a gas that has adsorbent properties for gases that are condensable and noncondensable at the temperature (e.g., adsorbent properties for hydrogen at 200 K). A method has also been proposed consisting of deposition of CO2 with

Firstly, this adsorbent gas deposition has the same disadvantages as solid adsorbents as described above, and secondly, as a result of an excess of injected gas or as a result of surface heating of pre-existing cryo-deposit. As a result, a pressure increase within the enclosure always occurs, and this pressure increase is generally undesirable.

The first objective of this invention is to provide a sorption cryopump with high pumping efficiency, i.e., highest pumping speed in molecular flow conditions and good protection of the adsorbent in viscous flow conditions or intermediate flow conditions. There is a particular thing.

A second object of this invention is to provide a lyopump in which adsorbent gas is injected, but pressure build-up within the enclosure during injection of adsorbent gas is prevented.

In order to achieve the above-mentioned button and other objects, the cryopump according to the invention comprises a partitioning device defining a localized area and having at least one partition, wherein said partition encloses the localized area. movable by actuation of a control device accessible from the outside of the enclosure from a closed position isolating it from the rest of the enclosure to an open position communicating the confined area with said remainder of the enclosure, the partitioning device being in the closed position displacing the adsorbent material. A layer is adapted to be located within the confined area.

According to this, the wall for trapping by adsorption is fully regenerated with all phases in preparation for it to finally act to trap the final residue of the gas, which is extremely difficult to condense. can be maintained.

Since this wall is not exposed to the highly condensable gases trapped by the condensation wall, the adsorption and trapping efficiency of the wall remains fully intact and undiminished.

The features and advantages of the invention will become apparent from the description of an embodiment that follows by way of example with reference to the drawings.

First, referring to FIGS. 1 and 2, the exhaust enclosure 1 (of which only the wall 201 portion is shown) is formed by a partition device 3 consisting of a number of vertical partitions (eight pieces) 4. The cryopump body is placed in the vertical partition 4.
extends between the end partitions 5 and 6 in an arrangement of polygonal contours.

Partition 4 is end partition 5. It is mounted so that its axis is a vertical axis determined by projections 7 and 8 that engage in pivot bearings provided at f, - and 6.

A ring 9 is mounted for rotation in the circumferential direction below the end partition 5 and can be rotated by a linkage 10 which penetrates the enclosure wall 2 by means of a sealing connection 11.

The ring 9 is fixed to a circumferentially pivoted part 12 and this part 1
2 is connected to each partition 4 by a hinge link 13.

According to this, by pulling the link mechanism 10 in the direction of the arrow fe starting from the fully closed position shown in FIG. A rotational opening movement takes place, resulting in extensive communication between the local area enclosed by the partitions 4, 5.6 in the closed position and the rest of the enclosure 1.

The partition 4 has special metallic properties and preferably consists of a thermally conductive metal.

It is coated on only one side with a layer 14 of adsorbent material, which is generally formed of particles of activated carbon or zeolite glued to the metal surface or embedded within the metal.

A cooling member such as a welded tube transports the helium at 20° to allow the partition 4 to be cooled.

For this embodiment, the inner surface of the partition (FIG. 1) and its adsorbent material coating 14 form a wall for trapping by adsorption, while the outer surface of the same partition 4, which does not have a coating, condenses. form a wall for capture.

The cryopump described above operates as follows.

The chamber to be evacuated (not shown) and the cryopump are first evacuated by a mechanical pump to a primary vacuum (5.10 ”
evacuated to a pressure below Torr).

During this operation the cryosurface formed by the partition→device 3 is in the open position (FIG. 2).

The cryopump is then cooled and the partition device 3 is moved to the closed position (FIG. 1).

The chamber is then evacuated by cryopumping and the condensable gas is trapped by the non-adsorbing outer surface 16 of the partition 4.

The critical vacuum thus obtained is equal to the vacuum obtained by cryopumping and depends on the amount of noncondensable gas in the chamber to be evacuated.

The linkage 10 can then be actuated to pivot the partition 4 as the non-condensable gas is released to reduce the residual level of non-condensable gas or by experiments carried out in the chamber.

Thus, the adsorbent initially applied to what was the inner surface 14 of the partition 4 can communicate with the enclosure 1 and become the main factor in the pumping action.

The opening angle of the partition 4 can be adjusted, so that the pumping speed for the gas to be adsorbed and the level of contamination by other gases can be varied simultaneously.

In the variant embodiment shown in FIGS. 3 and 4, the geometry of the partition device 3 is the same, but in this case the inner surface of the partition 4 has a permanently attached adsorbent material. When the partition 4 is in the closed position (Fig. 3), each of the partitions 4 has a hollow shaft 3.
It faces many slots 30 formed around the periphery of 1.

The interior of the hollow shaft 31 communicates with a duct 32 connected to a pressurized gas source (not shown) located outside the cryopump.

The operation of the modified embodiment is as described above with the following exceptions.

Thus, in this variant, the adsorbent gas is channeled through the slot 31 to effect the trapping by adsorption in the final stage before the partition 4 is opened, although the wall for trapping by adsorption comes into play. Immediately condenses as shown at 33 on the inner surface of the wall 4.

Once the gas is deposited, the linkage 10 is actuated to rotate the wall 4 as described above.

Also in the modified embodiments of FIGS. 5 and 6, the partition 50
(8) arranged in a polygonal profile, the inner surface 51 of which is coated with adsorbent material and the outer surface 52 is uncoated.

The partition 50 is hinged on a shaft 53 and can be pivoted open through a 90° angle by means of a linkage 10.

The linkage 10 passes through the closed connection 11 of the enclosure 2,
It is also connected to the shaft 53 via a chino 56 that engages with a sprocket 57 .

In this case, the surface for trapping by suction is considerably thickened by providing an equal number of radial partitions 54, which extend from the solid shaft 55 to the immediate vicinity of the partitions 50.

These radial partitions 54 are coated on both sides with adsorbent material.

The application aspect of this idea is to use it where high pumping speeds and clean high vacuums are required, especially where large amounts of non-condensable gases are liberated (e.g. hydrogen in thin film production, controlled neutron fusion, etc.). It is used for places.

The most well-known example of such an application is in thin film deposition equipment, where a return to atmospheric pressure is often performed, resulting in a viscous state (5.10"-10-4). A lot of driving time.

This invention virtually overcomes all the drawbacks associated with a return to atmospheric pressure.

The saturation of the adsorbent (in the case of solid adsorbents) in this case depends only on the amount of noncondensable gas released during the deposition.

[Brief explanation of the drawing]

FIG. 1 is a diagrammatic partial perspective view showing a cryopump according to the invention in an initial pumping stage with a part removed; FIG. 2 is a diagram showing the cryopump shown in FIG. 1 in a final pumping stage; 3 and 4 are the first modified embodiments.
FIGS. 5 and 6, corresponding to FIG. 2, are detailed elevational and detailed plan views of a control device suitable for another variant embodiment of the cryopump. In the drawings, 1 is an enclosure, 3 is a partition device, 4 is a vertical partition, 5 and 6 are end partitions, 10' is a link mechanism, 14
30 is a layer of adsorbent material, 30 is a slot, 3F is a hollow shaft, 50 is a partition, and 54 is a radial partition.

Claims (1)

[Claims for Utility Model Registration] 1) A thermally insulated cooling trapping device having a wall for trapping by condensation and a wall for trapping by adsorption coated with at least one layer of adsorbent material. a cryopump disposed within an enclosure, comprising a partitioning device defining a localized area and having at least one partition, said partition enclosing the localized area from a closed position separating the localized area from the remainder of the enclosure; an open position in communication with the rest of the body, movable by actuation of a control device accessible from outside the enclosure, such that when the partition device is in the closed position, a layer of adsorbent material is located within the confined area; A cryopump featuring: 2) A utility model application in which at least one of the walls for trapping by adsorption is formed by a partitioning device, the side of which is located near the localized area of the partitioning device being coated with a layer of adsorbent material. The cryopump according to item 1 in the range. 3) Utility model registration claim in which the layer of adsorbent material is formed by condensed adsorbent gas, and the device for introducing this gas extends from the outside of the cryopump enclosure into the interior of the localized adsorption zone. The cryopump according to item 1. 4) The partitioning device is broadly cylindrical and formed by a number of longitudinal partitions arranged polygonally between two stationary end partitions, the longitudinal partitions being movable about their central longitudinal pivot axis; The cryopump according to claim 1, which can be registered as a utility model. 5) The cryopump according to claim 1, wherein the control device for controlling the movable partition is a link mechanism that slides vertically within a sealed passage through the wall of the cryopump enclosure. 6) Practical use in which the device for introducing the adsorbent gas has openings that extend remotely from the end of the confined area and are distributed facing a partition for trapping by adsorption within the confined area. The cryopump according to claim 3 of the patent registration claim. 7) A cryopump according to claim 1, wherein the walls for trapping by adsorption include an array of radial walls extending into a confined area of broadly cylindrical shape.